1. Field of Invention
The present invention is related to a battery charging balancing system and a method thereof. Particularly, the present invention is related to a battery charging balancing system and a method thereof based on a battery operation process thereof by selecting a state of charge (SOC) estimation method according to the battery operation process.
2. Related Art
Recently, as prevalence and vigorous development of mobile devices, it has been very common to use battery charging balancing technique for increasing lifetime of a secondary battery. Hence, it is quite an issue to promote the battery charging balancing efficiency for the relevant product fields.
Generally, the charging balancing technique includes two main parts, i.e. active balancing and passive balancing. To effectively promote the charging balancing efficiency, it is a general measure to estimate a residual amount of the cell as a reference for charging balancing control. Hence, the charging balancing efficiency is greatly affected by the SOC of the battery. If the SOC of the battery cannot be accurately estimated, the cells in the battery assembly may not be effectively subject to the charging balancing, results in an overly charging issue of the cells due to the poor charging efficiency. This may even causes a reduction of the lifetime of the secondary battery.
In view of this, some factories have proposed ways to estimate the SOC for various batteries, such as the open circuit voltage method, ampere-hour method, Coulomb counting method, Carmen wave filtering method. There are even some methods proposed to improve the above methods for more accurate estimation, such as the improved Coulomb counting method derived from the Coulomb counting method. However, the estimation methods previously applied on such secondary battery might not be still suitable to the battery after various operations process. For example, after a long use of the secondary battery, the ampere-hour method for estimation of the SOC may get distorted with the use time of the battery. Therefore, the SOC estimation methods and the improved versions thereof still have the issue of poor charging balancing caused from the inaccurate estimation of the SOC, and need to be well addressed.
In view of the above, there is a need to overcome the long existing issue of poor charging balancing caused from the inaccurate estimation of the SOC, by setting forth an effective technique.